Beauty in the eye of the beholder?

HE EMERGED FROM THE METRO AT THE L’ENFANT PLAZA STATION AND POSITIONED HIMSELF AGAINST A WALL BESIDE A TRASH BASKET. By most measures, he was nondescript: a youngish white man in jeans, a long-sleeved T-shirt and a Washington Nationals baseball cap. From a small case, he removed a violin. Placing the open case at his feet, he shrewdly threw in a few dollars and pocket change as seed money, swiveled it to face pedestrian traffic, and began to play. (washingtonpost.com)

And hardly anyone took notice.

IF A GREAT MUSICIAN PLAYS GREAT MUSIC BUT NO ONE HEARS . . . WAS HE REALLY ANY GOOD?

It’s an old epistemological debate, older, actually, than the koan about the tree in the forest. Plato weighed in on it, and philosophers for two millennia afterward: What is beauty? Is it a measurable fact (Gottfried Leibniz), or merely an opinion (David Hume), or is it a little of each, colored by the immediate state of mind of the observer (Immanuel Kant)?